1. Field of the Invention
The invention relates to a sliding element with a support element and a sliding layer, between which a bearing metal layer is arranged, wherein the sliding layer is made from bismuth or a bismuth alloy and wherein the crystallites of the bismuth or the bismuth alloy in the sliding layer adopt a preferred direction with respect to their orientation, expressed by the Miller index of the lattice plane (012), wherein the X-ray diffraction intensity of the lattice plane (012) is the greatest compared to the X-ray diffraction intensity of the other lattice planes, and a method for its production.
2. Prior Art
Sliding bearings are characterised inter alia in that they have a relatively soft sliding layer in order to allow for adjustment to the supported element, for example a shaft, and to a certain degree to enable foreign particles to become embedded. In order to provide these tribological properties so far mainly sliding bearings containing tin or lead have been proposed in the prior art. However, lead is undesirable due to its toxicity and, particularly recently, increasing attempts have been made to find ways of eliminating lead.
Thus in DE 100 32 624 A a sliding bearing was proposed which comprises a bearing metal and a running layer made of bismuth or a bismuth alloy formed on the bearing metal, wherein the relative ratio of the X-ray diffraction intensity I[hkl] of the running layer made of bismuth or a bismuth alloy defined below satisfies the following conditions (a) and (b):
(a) the relative ratio of the X-ray diffraction intensity I[hkl] of other planes than {012} is 0.2 to 5 times as high as the ratio of the X-ray diffraction intensity I[012], i.e. 0.2 I[012]≦I[hkl]≦5 I[012];
(b) the relative ratio of the X-ray diffraction intensity I[hkl] of three or more other planes than {012} falls within a range which is 0.5 to 2 times as high as the relative ratio of the X-ray diffraction intensity I[012], i.e. 0.5 I[012]≦I[hkl]≦I[012],
wherein the {hkl}-planes of bismuth crystals of standard powder samples, which have a random orientation, show the X-ray diffraction intensity Rp(hkl); {hkl}-planes of bismuth crystals of the running layer made of bismuth or a bismuth alloy show the X-ray diffraction intensity R0/L(hkl); the ratio of the two intensities is expressed by K(hkl)=R0,L(hkl)Rp(hkl); the ratio of K(012) and K(hkl) is expressed by I[hkl]=K(hkl)/K(012).
Furthermore, from DE 10 2004 015 827 A a sliding element is known which comprises a rear metal layer, a sliding alloy layer provided on the rear metal layer and a cover layer provided on the sliding alloy layer, wherein the cover layer is made from bismuth or a bismuth alloy, and wherein in a crystal lattice of the cover layer a surface defined by Miller index (202) has a degree of orientation, which is not lower than 30%, and the X-ray diffraction intensity R(202) of the (202)-surface has a maximum value in comparison to other surfaces.